Abstract: Objective: To correlate active oxygen metabolism and water migration with fruit firmness in fresh Lingwuchangzao jujube during storage. Methods: The relative electrical conductivity (REC), malondialdehyde (MDA) content, hydrogen peroxide (H2O2) content and hardness of jujube fruit were measured during storage at room temperature (25 ℃) or 4 ℃, and the water migration and content were determined by low-field nuclear magnetic resonance (LF-NMR). Result: The accumulation of H2O2 and MDA and REC showed an upward trend with increasing storage time, and changed more significantly at room temperature than 4 ℃ (P < 0.05). REC increased rapidly after the 8th and 12th day storage at 25 and 4 ℃, respectively. In addition, the membrane structure was destroyed, and H2O2 and MDA were accumulated in large amounts. Analyses of water migration and relaxation areas of different water states revealed that the states of water molecules were mutually transformed into each other as storage proceeded. In general, total relaxation area (A2) and free water relaxation area (A23) showed a significant downward trend during storage at the two temperatures, and the trends were consistent with each other. A22 first rose and then fell. A21 showed a downward trend and an upward and then downward trend at 25 and 4 ℃, respectively. Conclusion: The rate of water loss from fresh jujubes stored at 4 ℃ was slower than that from those stored at room temperature (P < 0.05). Fruit hardness decreases with storage time. The texture quality of fresh jujubes stored at room temperature was significantly lower than that of fresh jujubes stored at 4 ℃ (P < 0.05). Correlation analysis and path analysis results showed that A21, MDA, A23 and REC significantly affected the firmness of fresh jujube fruit. This study may provide a theoretical basis for the storage and preservation of fresh Lingwuchangzao jujubes.

Key words: Lingwuchangzao jujube; active oxygen species; water migration; softening